1. Field of the Invention
The present invention relates to an optical disk cartridge for DVD-RAMs (digital versatile disk RAMs), and more particularly, relates to an optical disk cartridge suitable for use with 80 mm disks.
2. Description of the Related Art
Some optical disks, such as some CDs and DVDS, used while being accommodated in an optical disk cartridge.
A conventional disk cartridge for accommodating therein large (120 mm) disks will be described with reference to FIGS. 30 and 31.
Top and bottom faces of a casing 21 are formed with clamping windows 21a opposing the center of the casing 21, and are formed with reading and writing windows 21b connected to the clamping windows 21a. 
Each of the clamping windows 21a consists of a semicircular portion (R1 is about 17 mm) and a portion connected from the circular portion to each of the reading and writing windows 21a. 
When an optical disk cartridge is loaded on a disk driving apparatus 22, as shown in FIG. 31, a shutter is moved to open the clamping windows 21a and the reading and writing windows 21b. 
When the disk D is loaded, a table 23 enters into the clamping window 21a formed in the bottom face of the casing 21, and a clamper (not shown) enters into the clamping window 21a formed in the top face of the casing 21, whereby the disk D in the casing 21 is clamped while being slightly raised.
An optical head 24 is moved along the reading and writing windows 21b, whereby information is read from the disk D and is written on the disk D.
In order to smoothly insert the table 23 and the clamper into the clamping windows 21a, it is necessary to form opening areas of the clamping windows 21a larger than the table 23 or the clamper with clearance therebetween.
In particular, in an optical disk cartridge in which the table 23 is rotated about a fulcrum 25 to enter the clamping windows 21a, as shown in FIG. 31, a terminal edge 26 of the table 23 easily interferes with the peripheries of the clamping windows 21a, and it is necessary to form the clamping windows 21a larger than the table 23 with sufficient clearance.
According to an optical disk cartridge for accommodating therein small (80 mm) disks, it is difficult to form large (equivalent to 120 mm) clamping windows 21a. If the clamping windows 21a are enlarged, the width of the shutter for closing the clamping windows 21a is correspondingly increased, and side edges of the shutter may be extruded from the casing 1 when the shutter is slid to an opening position.
Accordingly, it is an object of the present invention to provide an optical disk cartridge which can form a large clamping window while preventing a shutter at an opening position from being extruded from a casing.
In accordance with the present invention, there is provided an optical disk cartridge including a casing having a pair of walls for accommodating an optical disk therein; wherein the walls of the casing are formed with clamping windows for clamping the disk at the central portions thereof, and are formed with reading and writing windows for reading information from the disk and writing information on the disk from the clamping windows to side edges of the casing; a shutter capable of opening and closing the clamping windows and the reading and writing windows is slidably provided, and the horizontal size of the clamping windows along a sliding direction of the shutter is formed shorter than the vertical size thereof orthogonal to the sliding direction of the shutter.
In the optical disk cartridge of the present invention, the clamping windows may be formed by linear parts opposing along the sliding direction of the shutter, and arcuate parts connecting the linear parts, and a distance between the linear parts may be shorter than a diameter of the arcuate parts.
In addition, the diameter of the arcuate parts of the clamping windows may be xc2x12 mm of 28 mm, and the distance between the linear parts may be xc2x12 mm of 27.4 mm.
In the optical disk cartridge of the present invention, projections for narrowing the width of the reading and writing windows may be formed on the border of the clamping windows and the reading and clamping windows.